In recent years, the utilization of wireless communication systems for communicating telephonically has achieved astonishing popularity. Conventional, voice communications as well as data communications can be effected telephonically through the use of such wireless communication systems.
In a wireless communication system, the communication channel formed between a sending and a receiving station is a radio channel, operating in a portion of the electromagnetic spectrum. A wire line connection is not required to effectuate the communication of a communication signal between the sending and receiving stations. Thus, communication via a wireless communication system is possible at locations to which formation of a wire line connection would be impossible or otherwise impractical.
Cellular communication systems have been implemented using various communication schemes. Cellular communication systems have been developed which utilize, for example, FDMA (frequency-division, multiple-access), TDMA (time-division, multiple-access), and CDMA (code-division, multiple-access) techniques, as well as various combinations of such techniques. A cellular communication system includes network infrastructure including a number of separated base transceiver stations, formed of fixed-site radio transceivers. Users communicate with the infrastructure of a cellular communication network through the use of a radio telephone or other communicator, typically referred to as a mobile station. The mobile station receives downlink signals on a forward link and transmits uplink signals on a reverse link. In this manner, bidirectional communications are provided between the infrastructure of the cellular communication network and the mobile station.
For the successful operation of a cellular communication system, synchronization is required between mobile stations and the base transceiver station. Such synchronization generally comes in two forms, including frequency synchronization and time synchronization of the frames and bits. Frequency synchronization is needed in order to ensure that the mobile station is synchronized to the carrier frequency of the BTS. Bit and frame synchronization provides adjustment of the propagation time differences of signals from different mobile stations so that transmitted “bursts” are received synchronously with the time slots of the base transceiver station, and so bursts in adjacent time slots do not overlap. Bit and frame synchronization is also required for the frame structure due to a higher-level superimposed frame structure for mapping logical signaling channels onto a physical channel.
Furthermore, when a mobile terminal is operating in a cellular communication system, it has to be synchronized to neighboring cells. In order to do this, the mobile station attempts to receive synchronization channels such as Frequency Correction Channels (FCCH) and Synchronization Channels (SCH) of the neighboring cells at certain intervals. On traffic channels, most of the TDMA frames are used for transferring data or speech, and limited available frames exist in which such synchronization information may be received. Partial searches can be performed at different frames to collectively provide the desired search result. However, within any given available frame, the number of time slots available are also limited, which can further spread out the searching operation unless enough consecutive times slots can be made available to account for all of the possible places in time that a synchronization signal such as an FCCH can present itself.
With the introduction of higher-level multislot classes, the consecutive time slots associated with a frame and available for receiving neighboring cell synchronization information becomes prohibitively limited. In many cases, there are not enough time slots to cover the range of times in which an FCCH or other synchronization signal can be presented, and the receipt of FCCH information must carry over to subsequent frames. This can cause significant delays and adversely affect communication throughput.
One prior art manner that addresses this is described in 3GPP TS 05.08, V8.14.0 (2002-04), “3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Radio Subsystem Link Control” (Release 1999), which is incorporated herein in its entirety. This specification indicates that the MS may skip receive operations for neighbor reception purposes. This results in the Rx operation after the idle frame being skipped to provide the requisite time slots for receiving the FCCH and SCH information. While this may not be necessary for unidirectional downlink data transfer (e.g., where sufficient downlink time slots are allocated), unnecessary breaks in the downlink and/or uplink data transfer can occur when skipping Rx operations during unidirectional uplink and bidirectional uplink/downlink data transfer. When using Uplink State Flag (USF), for example, for allocation of uplink resources, this decreases throughput for both downlink and uplink data transfers, since a permission to send uplink data is received in a downlink data block. By skipping Rx operations in the downlink direction, this permission to send uplink data may be missed, causing further delays. This problem is exacerbated when extended dynamic allocation or USF granularity (or both) are used, since one Rx block may provide permission to send multiple Tx blocks.
Accordingly, there is a need in the communications industry for a manner of receiving neighbor cell synchronization information that minimizes the impact of widening the associated search window. The present invention fulfills these and other needs, and offers other advantages over the prior art.